U.S. patent number 8,740,822 [Application Number 12/935,725] was granted by the patent office on 2014-06-03 for walking assist device.
This patent grant is currently assigned to Honda Motor Co., Ltd.. The grantee listed for this patent is Jun Ashihara, Yutaka Hiki, Zenta Sugawara. Invention is credited to Jun Ashihara, Yutaka Hiki, Zenta Sugawara.
United States Patent |
8,740,822 |
Hiki , et al. |
June 3, 2014 |
Walking assist device
Abstract
An actuator is reduced in weight without impairing a walking
assist function, and this reduces the inertial moment of a leg
link. A drive crank arm on the output shaft of the actuator and a
driven crank arm fixed to a second link portion so as to be
concentric to the joint shaft of a third joint portion are
connected to each other via a connection link. The connection link
is placed so that a line connecting a pivot portion at which the
drive crank arm is pivotally mounted and a pivot portion at which
the driven crank arm is pivotally mounted obliquely crosses a line
connecting the output shaft of the actuator and the joint shaft of
the third joint portion.
Inventors: |
Hiki; Yutaka (Wako,
JP), Sugawara; Zenta (Wako, JP), Ashihara;
Jun (Wako, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hiki; Yutaka
Sugawara; Zenta
Ashihara; Jun |
Wako
Wako
Wako |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
Honda Motor Co., Ltd. (Tokyo,
JP)
|
Family
ID: |
41135051 |
Appl.
No.: |
12/935,725 |
Filed: |
February 6, 2009 |
PCT
Filed: |
February 06, 2009 |
PCT No.: |
PCT/JP2009/000461 |
371(c)(1),(2),(4) Date: |
September 30, 2010 |
PCT
Pub. No.: |
WO2009/122641 |
PCT
Pub. Date: |
October 08, 2009 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20110028874 A1 |
Feb 3, 2011 |
|
Foreign Application Priority Data
|
|
|
|
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Apr 1, 2008 [JP] |
|
|
2008-095244 |
|
Current U.S.
Class: |
601/35; 601/33;
602/16; 601/5; 602/23 |
Current CPC
Class: |
A61H
3/00 (20130101); A61H 1/024 (20130101); A61H
3/008 (20130101); A61H 2201/1215 (20130101); A61H
2201/1623 (20130101); A61H 2201/1633 (20130101); A61H
2201/5061 (20130101); A61H 2201/5071 (20130101); A61H
2201/165 (20130101); A61H 2201/1436 (20130101); A61H
2201/1642 (20130101); A61H 2201/1635 (20130101); A61H
2201/1676 (20130101) |
Current International
Class: |
A61H
3/00 (20060101) |
Field of
Search: |
;601/5,23,33,34,35
;602/5,16,19,23,26,27 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
|
5476441 |
December 1995 |
Durfee et al. |
5658242 |
August 1997 |
McKay et al. |
6666796 |
December 2003 |
MacCready, Jr. |
|
Foreign Patent Documents
|
|
|
|
|
|
|
62-045419 |
|
Mar 1987 |
|
JP |
|
06-114089 |
|
Apr 1994 |
|
JP |
|
09-210048 |
|
Aug 1997 |
|
JP |
|
3074203 |
|
Oct 2000 |
|
JP |
|
2007-020909 |
|
Feb 2007 |
|
JP |
|
2007-315920 |
|
Dec 2007 |
|
JP |
|
2008-012224 |
|
Jan 2008 |
|
JP |
|
Primary Examiner: Thanh; Quang D
Attorney, Agent or Firm: Rankin, Hill & Clark LLP
Claims
What is claimed is:
1. A walking assist device which is provided with a load transmit
portion, a foot mounting portion adapted to be mounted to a user's
foot, and a leg link disposed between the load transmit portion and
the foot mounting portion, the walking assist device being
configured to transmit a force generated from the leg link to the
user's trunk via the load transmit portion, and the leg link
including an upper first link portion connected to the load
transmit portion via a first joint portion, a lower second link
portion connected to the foot mounting portion via a second joint
portion, a middle third joint portion connected to the first link
portion and the second link portion in such a way that the first
link portion and the second link portion can stretch and bend
freely, and a drive mechanism to drive the third joint portion,
wherein the drive mechanism is provided with a rotary actuator
mounted to the first link portion, a drive crank arm disposed on an
output shaft of the rotary actuator, a driven crank arm fixed to at
the second link portion concentrically to a joint shaft of the
third joint portion, and a connection link with one end pivoted at
the drive crank arm and the other end pivoted at the driven crank
arm, and the connection link is disposed in such a way that a
connection line connecting a pivot portion of the connection link
at which the drive crank arm is pivotally mounted and a pivot
portion of the connection link at which the driven crank arm is
pivotally mounted obliquely crosses a connection line connecting
the output shaft of the rotary actuator and the joint shaft of the
third joint portion.
2. The walking assist device according to claim 1, wherein the load
transmit portion is composed of a seat member adapted for the user
to sit astride, the first joint portion is composed of an
arc-shaped guide rail which is connected to the seat member and is
longitudinal in an anteroposterior direction with a center of
curvature located above the seat member and a slider which is fixed
at an upper portion of the first link portion and is movably
engaged in the guide rail, the slider is engaged to a part of the
guide rail which is positioned at a front side or a rear side to a
connection line connecting the center of curvature of the guide
rail and the joint shaft of the third joint portion, and the pivot
portion of the connection link at which the drive crank arm is
pivotally mounted is disposed opposite to the guide rail with
respect to the connection line connecting the output shaft of the
rotary actuator and the joint shaft of the third joint portion.
3. The walking assist device according to claim 2, wherein the
first link portion is provided with an accessory member at a
position closer to the guide rail than to the connection line
connecting the output shaft of the rotary actuator and the joint
shaft of the third joint portion.
Description
PRIORITY CLAIM
The present application is based on and claims the priority benefit
of Japanese Patent Application 2008-095244 filed on Apr. 1, 2008,
the contents of which are incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a walking assist device for
assisting a user in walking.
2. Description of the Related Art
Conventionally, as a walking assist device, there has been known
one provided with a load transmit portion, a foot mounting portion
mounted to a user's foot, and a leg link disposed between the load
transmit portion and the foot mounting portion (for example, refer
to Patent Document 1: Japanese Patent Laid-Open No. 2007-20909).
The walking assist device is configured to transmit a force
generated from the leg link to the user's trunk via the load
transmit portion.
The leg link in the walking assist device includes an upper first
link portion connected to the load transmit portion via a first
joint portion, a lower second link portion connected to the foot
mounting portion via a second joint portion, a middle third joint
portion connected to the first link portion and the second link
portion in such a way that the first link portion and the second
link portion can stretch and bend freely, and a drive mechanism to
drive the third joint portion.
Thereby, the load applied to a leg of the user can be alleviated
according to the force generated by the drive mechanism in the
direction of decreasing a flexion angle of the third joint portion
(same as the direction of stretching the leg link).
In the device disclosed in Patent Document 1, the load transmit
portion is composed of a seat member on which the user sits
astride, and the first joint portion is composed of an arc-shaped
guide rail which is connected to the seat member and is
longitudinal in an anteroposterior direction with the center of
curvature located above the seat member and a slider which is fixed
at an upper end portion of the first link portion and is movably
engaged in the guide rail.
Thereby, the center of curvature of the guide rail is equivalent to
the swing fulcrum for the leg link of the first joint portion in
the anteroposterior direction. Since the swing fulcrum is located
above the seat member, the seat member can be prevented from
inclining greatly in the vertical direction due to the shifting in
the weight of the user.
Further, in the device disclosed in Patent Document 1, the slider
is engaged to a part of the guide rail which is positioned at a
rear side to the connection line connecting the center of curvature
of the guide rail and the joint shaft of the third joint portion.
Thereby, the swing stroke of the leg link to the forward so as to
follow the forward movement of a free leg (the leg with foot
leaving away from the floor) of the user can be assured without
increasing the length of the guide rail to the forward direction
too much; consequently, it is expected to reduce the size of the
first joint portion.
The drive mechanism described in an embodiment of the Patent
Document 1 is provided with a rotary actuator mounted to the first
link portion, and a wire-typed force transmit portion configured to
transmit a force from the rotary actuator to the third joint
portion via a wire. However, the drive mechanism is not limited
thereto, specifically, it is acceptable that the drive mechanism is
provided with the rotary actuator mounted to the first link
portion, a drive crank arm disposed on an output shaft of the
rotary actuator, a driven crank arm fixed to at the second link
portion concentrically to a joint shaft of the third joint portion,
and a connection link with one end pivoted at the drive crank arm
and the other end pivoted at the driven crank arm.
Generally, it has been considered to configure the drive mechanism
as a parallel link mechanism by disposing the connection link in
such a way that a connection line connecting a pivot portion of the
connection link at which the drive crank arm is pivotally mounted
and a pivot portion of the connection link at which the driven
crank arm is pivotally mounted is parallel to a connection line
connecting the output shaft of the rotary actuator and the joint
shaft of the third joint portion.
However, if the inertial moment of the leg link around the first
joint portion is greater, when the user swings the free leg to the
forward, the load applied to the free leg due to the inertial
moment of the leg link will become greater. Therefore, it is
desired to reduce the inertial moment of the leg link. In this
regarding, if the rotary actuator mounted at the first link portion
is made lighter, the inertial moment of the leg link can be
reduced. However, in order to generate the desired assist force for
the leg link, it is necessary for the rotary actuator to output a
torque of at least a certain magnitude; therefore, there is a limit
on reducing the weight of the rotary actuator.
To solve this problem, it has been considered to increase the
length of the driven crank arm longer than the length of the drive
crank arm to decrease the rotational angular velocity of the driven
crank arm slower than the rotational angular velocity of the drive
crank arm so as to increase the torque transmitted to the driven
crank arm, in other words, to increase the drive torque of the
third joint portion greater than the output torque of the rotary
actuator. However, this solution brings about the following
problem, that is, for the leg link with the first link portion and
the second link portion connected by the third joint portion in
such a way that the first link portion and the second link portion
can stretch and bend freely, the telescopic velocity of the leg
link obtained by differentiating the length of the leg link (the
length of a line segment connecting the first joint portion at the
upper end and the second joint portion at the lower end) by the
flexion angle of the third joint portion slows down as the flexion
angle of the third joint portion decreases. Therefore, in order to
improve the controllability in a small range of the flexion angles
of the third joint portion, it is necessary to make the flexion
angle vary faster. Accordingly, in the device where the rotational
angular velocity of the driven crank arm is slower than the
rotational angular velocity of the drive crank arm, the required
rotational velocity of the rotary actuator would be greater, which
makes it difficult to reduce the weight of the rotary actuator.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the
aforementioned problems, and it is therefore an object of the
present invention to provide a walking assist device capable of
alleviating the inertial moment of a leg link through reducing the
weight of a rotary actuator without impairing a walking assist
function thereof.
To attain an object described above, a walking assist device
according to the present invention is provided with a load transmit
portion, a foot mounting portion mounted to a user's foot, and a
leg link disposed between the load transmit portion and the loot
mounting portion, the walking assist device being configured to
transmit a force generated from the leg link to the user's trunk
via the load transmit portion, and the leg link including an upper
first link portion connected to the load transmit portion via a
first joint portion, a lower second link portion connected to the
foot mounting portion via a second joint portion, a middle third
joint portion connected to the first link portion and the second
link portion in such a way that the first link portion and the
second link portion can stretch and bend freely, and a drive
mechanism to drive the third joint portion, wherein the drive
mechanism is provided with a rotary actuator mounted to the first
link portion, a drive crank arm disposed on an output shaft of the
rotary actuator, a driven crank arm fixed to at the second link
portion concentrically to a joint shaft of the third joint portion,
and a connection link with one end pivoted at the drive crank arm
and the other end pivoted at the driven crank arm, and the
connection link is disposed in such a way that a connection line
connecting a pivot portion of the connection link at which the
drive crank arm is pivotally mounted and a pivot portion of the
connection link at which the driven crank arm is pivotally mounted
obliquely crosses a connection line connecting the output shaft of
the rotary actuator and the joint shaft of the third joint
portion.
According to the present invention, since the connection line
connecting the pivot portion of the connection link at which the
drive crank arm is pivotally mounted and the pivot portion of the
connection link at which the driven crank arm is pivotally mounted
obliquely crosses the connection line connecting the output shaft
of the rotary actuator and the joint shaft of the third joint
portion, the ratio between the rotational angular velocity of the
driven crank arm and the rotational angular velocity of the drive
crank arm varies according to the rotation angle of the drive crank
arm. Further, in a flexion angle range of the third joint portion
when the user is in normal walking (walking on a flat floor), the
rotational angular velocity of the driven crank arm is made slower
than the rotational angular velocity of the drive crank arm so as
to obtain a torque amplifying effect to make the toque (the drive
torque of the third joint portion) transmitted to the driven crank
arm greater than the output torque from the rotary actuator.
According thereto, it is possible to increase the rotational
angular velocity of the driven crank arm greater than the
rotational angular velocity of the drive crank arm in a small range
of the flexion angles of the third joint portion. Thereby, it is
possible to increase only a small amount of amplified torque in the
output torque of the rotary actuator needed to generate the assist
force required in the normal walking. Thus, the required rotational
angular velocity of the rotary actuator can be inhibited lower with
only an increment on velocity so as to assure the controllability
in a small range of the flexion angles of the third joint portion.
Consequently, the weight of the rotary actuator can be reduced
without impairing the walking assist function. Thereby, the
inertial moment of the leg link around the first joint portion is
reduced, and the load applied to the free leg when the user swings
the free leg to the forward can be alleviated.
In the present invention, similar to Patent Document 1, the load
transmit portion is composed of a seat member on which the user
sits astride, the first joint portion is composed of an arc-shaped
guide rail which is connected to the seat member and is
longitudinal in an anteroposterior direction with the center of
curvature located above the seat member, and a slider which is
fixed at the upper portion of the first link portion and is movably
engaged in the guide rail, the slider is engaged to a part of the
guide rail which is positioned at a front side or a rear side to
the connection line connecting the center of curvature of the guide
rail and the joint shaft of the third joint portion, and it is
desirable that the pivot portion of the connection link at which
the drive crank arm is pivotally mounted is disposed opposite to
the guide rail with respect to the connection line connecting the
output shaft of the rotary actuator and the joint shaft of the
third joint portion. According thereto, without providing a motion
space for the drive crank arm and the connection link between the
output shaft of the rotary actuator and the guide rail, the
rotation shaft of the rotary actuator, namely, the center of
gravity of the rotary actuator can be positioned nearby the guide
rail. Moreover, a supporting force for supporting the weight of the
user, namely, the force in the direction of decreasing the flexion
angle of the third joint portion can be transmitted through the
tension of the connection link. Different from transmitting the
force through pushing, it is not necessary to enlarge the cross
sectional area of the connection link to prevent it from buckling,
which makes it possible to reduce the self weight of the connection
link. Consequently, the inertial moment of the leg link around the
first joint portion (around the center of curvature of the guide
rail) can be further alleviated.
Moreover, it is necessary to provide an accessory member such as a
battery in the first link portion. In this situation, as mentioned
above, the pivot portion of the connection link at which the drive
crank arm is pivotally mounted is disposed opposite to the guide
rail with respect to the connection line connecting the output
shaft of the rotary actuator and the joint shaft of the third joint
portion. Accordingly, the accessory member can be disposed at a
position at a portion of the first link portion where closer to the
guide rail than to the connection line connecting the output shaft
of the rotary actuator and the joint shaft of the third joint
portion without interfering with the connection link. Thereby, the
distance between the accessory member and the guide rail becomes
shorter, and resultantly, the inertial moment of the leg link
around the first joint portion can be prevented from increasing due
to the weight of the accessory member as much as possible.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a walking assist device according
to an embodiment of the present invention.
FIG. 2 is a side view of the walking assist device according to the
embodiment.
FIG. 3 is a front view of the walking assist device according to
the embodiment.
FIG. 4 is a partial cutaway side view of a first link portion of
the walking assist device according to the embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A walking assist device according to an embodiment of the present
invention will be described hereinafter. As illustrated from FIG. 1
to FIG. 3, the walking assist device includes a seat member 1 as a
load transmit portion on which a user P sits astride, a pair of
left and right foot mounting portions 2 and 2 which are attached to
user's left and right feet, respectively, and a pair of left and
right leg links 3 and 3 disposed between the seat member 1 and the
pair of left and right foot mounting portions 2 and 2.
Each leg link 3 is composed of an upper first link portion 5
connected to the seat member 1 via a first joint portion 4, a lower
second link portion 7 connected to the foot mounting portion 2 via
a second joint portion 6, a middle third joint portion 8 connected
to the first link portion 5 and the second link portion 7 in such a
way that the first link portion 5 and the second link portion 7 can
stretch and bend freely, and a drive mechanism 9 to drive the third
joint portion 8. Then, a force in the direction of stretching each
leg link 3 is applied to each leg link 3 from the third joint
portion 8 driven by the drive mechanism 9 to generate a supporting
force which supports at least a part of the user's weight
(hereinafter, referred to as assist force). The assist force
generated in each leg link 3 is transmitted to the trunk of the
user P via the seat member 1 to alleviate the load on the leg of
the user P.
The seat member 1 is composed of a seat portion 1a where the user P
sits, a support frame 1b, and a waist supporter 1c. The seat
portion 1a is of a saddle shape. The support frame 1b is disposed
below the seat portion 1a to support the seat portion 1a. The
support frame 1b is configured to extend upward behind the seat
portion 1a. The support frame 1b has an uprising portion at a rear
end thereof. The waist supporter 1c is fixed at the uprising
portion. The waist supporter 1c is provided with a holding portion
1d of an arch shape to be held by the user P if necessary.
The first joint portion 4 for each leg link 3 has an arc-shaped
guide rail 41 connected to the seat member 1. Then, each leg link 3
is movably engaged with the guide rail 41 via a plurality of
rollers 43 pivotally attached to a slider 42 which is fixed to the
upper end of the first link portion 5. Thereby, each leg link 3
swings in the anteroposterior direction around the center of
curvature 4a of the guide rail 41 and the anteroposterior swing
fulcrum of each leg link 3 with respect to the first joint portion
4 functions as the center of curvature 4a of the guide rail 41.
Furthermore, the guide rail 41 is pivotally supported at the
uprising portion formed at the rear end of the support frame 1b of
the seat member 1 via a spindle 4b which is longitudinal in the
anteroposterior direction. Thus, the guide rail 41 is connected to
the seat member 1, capable of swinging freely in the lateral
direction. According thereto, each leg link 3 is allowed to swing
in the lateral direction, which enables the user P to abduct the
legs thereof. In addition, the anteroposterior swing fulcrum of
each leg link 3 (the center of curvature 4a of the guide rail 41)
and the lateral swing fulcrum (the spindle) 4b are both located
above the seat portion 1a. Thereby, the seat member 1 can be
prevented from inclining greatly both in the vertical direction and
the lateral direction when the user P shifts the body weight
thereof.
The first link portion 5 is disposed to be inclined backward. The
slider 42 is engaged to a part of the guide rail 41 which is
positioned at a rear side to the connection line connecting the
center of curvature 4a of the guide rail 41 and a joint shaft 8a of
the third joint portion 8. Thereby, the swing stroke of the leg
link 3 to the forward so as to follow the forward movement of a
free leg of the user P can be assured without increasing the length
of the guide rail to the forward direction too much.
Each foot mounting portion 2 has a shoe 2a and a joint member 2b
protruding upward from the inside of the shoe 2a. The second link
portion 7 of each leg link 3 is connected to the joint member 2b
via the second joint portion 6 of a three-axis structure. As
illustrated in FIG. 2, a pair of longitudinally disposed pressure
sensors 10 and 10, which detect loads applied to the
metatarsophalangeal joint (MP joint) and the heel of each foot of
the user P, respectively, are attached to the undersurface of an
insole 2c provided in the shoe 2a. Moreover, a 2-axis force sensor
11 is built into the second joint portion 6. Detection signals from
the pressure sensors 10 and the force sensor 11 are input into a
controller 12 housed in the support frame 1b of the seat member 1.
On the basis of the detection signals from the pressure sensors 10
and the force sensor 11, the controller 12 performs a walking
assist control by controlling the driving source 9 to drive the
third joint portion 8 of the leg link 3 to generate the
above-mentioned assist force.
The assist force is applied on a connection line (hereinafter,
referred to as a reference line) joining a swing fulcrum 4a of the
leg link 3 with respect to the first joint portion 4 in the
anteroposterior direction and a swing fulcrum of the leg link 3
with respect to the second joint portion 6 in the anteroposterior
direction. In the walking assist control, the actual assist force
applied on the reference line (accurately, a resultant force
between the assist force and a force generated by the weights of
the seat member 1 and each leg link 3) is calculated based on
detection values of forces in the two-axis direction detected by
the force sensor 11. Thereafter, on the basis of the stepping force
detected by the pressure sensors 10 for each foot mounting portion
2, a ratio of the stepping force of each foot with respect to the
resultant force applied to both feet of the user P is calculated.
Then, a desired control value of the assist force which should be
generated in each leg link 3 is calculated by multiplying a
predefined value of the assist force by the calculated ratio of the
stepping force of each foot. Subsequently, the driving mechanism 9
is controlled so as to make the actual assist force calculated on
the basis of the detection values by the force sensor 11
approximate to the desired control value.
The drive mechanism 9 is provided with a rotary actuator 91 mounted
on the outer surface of the upper end portion of the first link
portion 5, a drive crank arm 92 disposed on an output shaft 91b of
the rotary actuator 91, a driven crank arm 93 fixed to at the
second link portion 7 concentrically to the joint shaft 8a of the
third joint portion 8, and a connection link 94 with one end
thereof pivoted at the drive crank arm 92 and the other end pivoted
at the driven crank arm 93. The rotary actuator 91 is composed of
an electric motor provided with a reduction gear 91a. As
illustrated in FIG. 4, the connection link 94 is disposed in such a
way that a connection line L2 connecting a pivot portion 94a of the
connection link 94 at which the drive crank arm 92 is pivotally
mounted and a pivot portion 94b of the connection link 94 at which
the driven crank arm 93 is pivotally mounted (hereinafter, referred
to as a floating link line) obliquely crosses a connection line L1
connecting the output shaft 91b of the rotary actuator 91 and the
joint shaft 8a of the third joint portion 8 (hereinafter, referred
to as a fixed link line).
When the floating link line L2 is obliquely crossed with the fixed
link line L1, a ratio between the rotational angular velocity of
the driven crank arm 93 and the rotational angular velocity of the
drive crank arm 92 varies according to the rotation angle of the
drive crank arm 92. In the present embodiment, when the flexion
angle .theta. of the third joint portion 8 (the angle formed
between the line passing through the third joint portion 8 and the
center of curvature 4a of the guide rail 41 and the line passing
through the third joint portion 8 and the second joint portion 6)
is in the range of about 20.degree. to 70.degree., the ratio of the
angular velocity between the driven crank arm 93 and the drive
crank arm 92 (the rotational angular velocity of the driven crank
arm 93/the rotational angular velocity of the drive crank arm 92)
is equal to or less then 1. When the ratio of the angular velocity
is equal to or less then 1, the torque transmitted to the driven
crank arm 93, namely the drive torque of the third joint portion 8
becomes equal to or greater than the output torque of the rotary
actuator 91.
When the user P is in normal walking (walking on a flat floor), the
flexion angle .theta. of the third joint portion 8 ranges from
about 40.degree. to 70.degree.. Thus, in the range of the flexion
angles of the third joint portion 8 when the user P is in normal
walking, the rotational angular velocity of the driven crank arm 93
is slower than the rotational angular velocity of the drive crank
arm 92. As a result thereof, in normal walking, a torque amplifying
effect is obtained to make the drive torque of the third joint
portion 8 greater than the output torque of the rotary actuator 91;
consequently, the output torque of the rotary actuator 91 needed to
generate the desired assist force is limited to the amount of the
amplified torque only.
The telescopic velocity of the leg link 3 obtained by
differentiating the length of the line segment between the swing
fulcrum 4a of the leg link 3 with respect to the first joint
portion 4 and the second joint portion 6 (the length of the leg
link) by the flexion angle .theta. of the third joint portion 8
slows down as the flexion angle .theta. decreases. In order to
improve the controllability in a small range of the flexion angles
.theta., it is necessary to make the flexion angle .theta. vary
faster. Accordingly, the required rotation velocity of the rotary
actuator 91 would be greater, which makes it difficult to reduce
the weight of the rotary actuator 91. To solve this problem, in the
present embodiment, the rotational angular velocity of the driven
crank arm 93 is made faster than the rotational angular velocity of
the drive crank arm 92 to gain the velocity increasing effect in
the range of flexion angles .theta. equal to or less than about
20.degree.. Thereby, the required rotational angular velocity of
the rotary actuator 91 can be inhibited lower with only the
increment on velocity so as to assure the controllability in a
small range of the flexion angles .theta..
Accordingly, in the present embodiment, according to the torque
amplifying effect in normal walking and the velocity increasing
effect in a small range of flexion angles .theta., the weight of
the rotary actuator 91 can be reduced without impairing a walking
assist function thereof. Thereby, the inertial moment of the leg
link 3 around the first joint portion 4 is reduced, and the load
applied to the free leg when the user P swings the tree leg thereof
to the forward can be alleviated.
In the present invention, the pivot portion 94a of the connection
link 94 at which the drive crank arm 92 is pivotally mounted is
disposed opposite to the guide rail 41 of the first joint portion 4
with respect to the fixed link line L1. According thereto, without
providing a motion space for housing the drive crank arm 92 and the
connection link 94 between the output shall 91b of the rotary
actuator 91 and the guide rail 41, the rotation shall 91b of the
rotary actuator 91, namely, the center of gravity of the rotary
actuator 91 can be positioned close to the guide rail 41.
Moreover, the assist force supporting the weight of the user P,
namely, the force in the direction of decreasing the flexion angle
.theta. of the third joint portion 8 can be transmitted from the
rotary actuator 91 to the third joint portion 8 through the tension
of the connection link 94. Different from transmitting the force
through pushing, it is not necessary to enlarge the cross sectional
area of the connection link 94 to prevent it from buckling, which
makes it possible to reduce the self weight of the connection link
94. Consequently, in addition to disposing the center of gravity of
the rotary actuator 91 close 10 the guide rail 41, the inertial
moment of the leg link 3 around the first joint portion 4 (around
the center of curvature 4a of the guide rail 41) can be further
alleviated.
Moreover, as mentioned above, the pivot portion 94a of the
connection link 94 at which the drive crank arm 92 is pivotally
mounted is disposed opposite to the guide rail 41 of the first
joint portion 4 with respect to the fixed link line L1.
Accordingly, a space can be assured in a portion of the first link
portion 5 closer to the guide rail 41 than to the fixed link line
L1 without interfering with the connection link 94. In the present
embodiment, the accessory member 13 such as the battery or the like
is disposed in the space. Thereby, the distance between the
accessory member 13 and the guide rail 41 becomes shorter, and
resultantly, the inertial moment of the leg link 3 around the first
joint portion 4 can be prevented from increasing due to the weight
of the accessory member 13 as much as possible. In addition, a
cover 51 covering the accessory member 13 is attached to the first
link portion 5.
Though the embodiment of the present invention has been described
as above, it is not limited thereto. For example, in the
above-mentioned embodiment, the slider 42 is engaged to a part of
the guide rail 41 which is positioned at a rear side than the
connection line connecting the center of curvature 4a of the guide
rail 41 and the joint shaft 8a of the third joint portion 8.
However, by bending the leg link 3 opposite to the one described in
the above-mentioned embodiment in the lateral direction, it is
acceptable to engage the slider 42 to a part of the guide rail 41
which is position at a front side than the connection line
connecting the center of curvature 4a of the guide rail 41 and the
joint shaft 8a of the third joint portion 8. In this case, by
disposing the pivot portion of the connection link 94 at which the
drive crank arm 92 is pivotally mounted opposite to the guide rail
41 with respect to the connection line connecting the output shaft
91b of the rotary actuator 91 and the joint shaft 8a of the third
joint portion 8, similar effect can be obtained as in the
above-mentioned embodiment.
In the embodiment mentioned above, the first joint portion 4 is
configured to have the guide rail 41 of an arc shape and the swing
fulcrum 4a of each leg link 3 in the anteroposterior direction with
respect to the first joint portion 4 is located above the seat
member 1. However, it is also possible to configure the first joint
portion 4 to a simple-structured joint portion having a spindle in
the lateral direction to pivotally support each leg link 3 so that
the upper end portion thereof can freely swing in the
anteroposterior direction. It is also acceptable to adopt a spring
mounted around the waist of the user as the load transmit portion.
Moreover, in order to assist the walking of a handicapped user
whose one leg is crippled due to bone fracture or the like, it is
possible to leave only one leg link of the left and right leg links
3 and 3 in the above-mentioned embodiment corresponded to the
crippled leg of the user by removing the other.
* * * * *